<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
<title>Parser</title>
<link rel="stylesheet" href="../../../../../../../../doc/src/boostbook.css" type="text/css">
<meta name="generator" content="DocBook XSL Stylesheets V1.75.0">
<link rel="home" href="../../../../index.html" title="Spirit 2.4">
<link rel="up" href="../parser_concepts.html" title="Parser Concepts">
<link rel="prev" href="../parser_concepts.html" title="Parser Concepts">
<link rel="next" href="primitiveparser.html" title="PrimitiveParser">
</head>
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
<table cellpadding="2" width="100%"><tr>
<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../../boost.png"></td>
<td align="center"><a href="../../../../../../../../index.html">Home</a></td>
<td align="center"><a href="../../../../../../../../libs/libraries.htm">Libraries</a></td>
<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
<td align="center"><a href="../../../../../../../../more/index.htm">More</a></td>
</tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="../parser_concepts.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../parser_concepts.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="primitiveparser.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a>
</div>
<div class="section">
<div class="titlepage"><div><div><h5 class="title">
<a name="spirit.qi.reference.parser_concepts.parser"></a><a class="link" href="parser.html" title="Parser">Parser</a>
</h5></div></div></div>
<a name="spirit.qi.reference.parser_concepts.parser.description"></a><h6>
<a name="id882346"></a>
<a class="link" href="parser.html#spirit.qi.reference.parser_concepts.parser.description">Description</a>
</h6>
<p>
The <span class="emphasis"><em>Parser</em></span> is the most fundamental concept. A Parser
has a member function, <code class="computeroutput"><span class="identifier">parse</span></code>,
that accepts a first-last <a href="http://www.sgi.com/tech/stl/ForwardIterator.html" target="_top"><code class="computeroutput"><span class="identifier">ForwardIterator</span></code></a> pair and returns
bool as its result. The iterators delimit the data being parsed. The
Parser's <code class="computeroutput"><span class="identifier">parse</span></code> member
function returns <code class="computeroutput"><span class="keyword">true</span></code> if
the parse succeeds, in which case the first iterator is advanced accordingly.
Each Parser can represent a specific pattern or algorithm, or it can
be a more complex parser formed as a composition of other Parsers.
</p>
<div class="variablelist">
<p class="title"><b>Notation</b></p>
<dl>
<dt><span class="term"><code class="computeroutput"><span class="identifier">p</span></code></span></dt>
<dd><p>
A <code class="computeroutput"><span class="identifier">Parser</span></code>.
</p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">P</span></code></span></dt>
<dd><p>
A <code class="computeroutput"><span class="identifier">Parser</span></code> type.
</p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">Iter</span></code></span></dt>
<dd><p>
a <a href="http://www.sgi.com/tech/stl/ForwardIterator.html" target="_top"><code class="computeroutput"><span class="identifier">ForwardIterator</span></code></a> type.
</p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">f</span></code>, <code class="computeroutput"><span class="identifier">l</span></code></span></dt>
<dd><p>
<a href="http://www.sgi.com/tech/stl/ForwardIterator.html" target="_top"><code class="computeroutput"><span class="identifier">ForwardIterator</span></code></a>. first/last
iterator pair.
</p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">Context</span></code></span></dt>
<dd><p>
The parser's Context type.
</p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">context</span></code></span></dt>
<dd><p>
The parser's Context, or <code class="computeroutput"><span class="identifier">unused</span></code>.
</p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">skip</span></code></span></dt>
<dd><p>
A skip Parser, or <code class="computeroutput"><span class="identifier">unused</span></code>.
</p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">attrib</span></code></span></dt>
<dd><p>
A Compatible Attribute, or <code class="computeroutput"><span class="identifier">unused</span></code>.
</p></dd>
</dl>
</div>
<a name="spirit.qi.reference.parser_concepts.parser.valid_expressions"></a><h6>
<a name="id882626"></a>
<a class="link" href="parser.html#spirit.qi.reference.parser_concepts.parser.valid_expressions">Valid
Expressions</a>
</h6>
<p>
In the expressions below, the behavior of the parser, <code class="computeroutput"><span class="identifier">p</span></code>,
and how <code class="computeroutput"><span class="identifier">skip</span></code> and <code class="computeroutput"><span class="identifier">attrib</span></code> are handled by <code class="computeroutput"><span class="identifier">p</span></code>, are left unspecified in the base
<code class="computeroutput"><span class="identifier">Parser</span></code> concept. These
are specified in subsequent, more refined concepts and by the actual
models thereof.
</p>
<p>
For any Parser the following expressions must be valid:
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Expression
</p>
</th>
<th>
<p>
Semantics
</p>
</th>
<th>
<p>
Return type
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
</p>
<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="identifier">p</span><span class="special">.</span><span class="identifier">parse</span><span class="special">(</span><span class="identifier">f</span><span class="special">,</span> <span class="identifier">l</span><span class="special">,</span> <span class="identifier">context</span><span class="special">,</span> <span class="identifier">skip</span><span class="special">,</span> <span class="identifier">attr</span><span class="special">)</span></pre>
<p>
</p>
</td>
<td>
<p>
Match the input sequence starting from <code class="computeroutput"><span class="identifier">f</span></code>.
Return <code class="computeroutput"><span class="keyword">true</span></code> if
successful, otherwise return <code class="computeroutput"><span class="keyword">false</span></code>.
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="keyword">bool</span></code>
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">p</span><span class="special">.</span><span class="identifier">what</span><span class="special">(</span><span class="identifier">context</span><span class="special">)</span></code>
</p>
</td>
<td>
<p>
Get information about a Parser.
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="identifier">info</span></code>
</p>
</td>
</tr>
</tbody>
</table></div>
<a name="spirit.qi.reference.parser_concepts.parser.type_expressions"></a><h6>
<a name="id882900"></a>
<a class="link" href="parser.html#spirit.qi.reference.parser_concepts.parser.type_expressions">Type
Expressions</a>
</h6>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Expression
</p>
</th>
<th>
<p>
Description
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">P</span><span class="special">::</span><span class="keyword">template</span> <span class="identifier">attribute</span><span class="special"><</span><span class="identifier">Context</span><span class="special">,</span> <span class="identifier">Iter</span><span class="special">>::</span><span class="identifier">type</span></code>
</p>
</td>
<td>
<p>
The Parser's expected attribute.
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">is_parser</span><span class="special"><</span><span class="identifier">P</span><span class="special">>::</span><span class="identifier">type</span></code>
</p>
</td>
<td>
<p>
Metafunction that evaluates to <code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">true_</span></code>
if a certain type, <code class="computeroutput"><span class="identifier">P</span></code>
is a Parser, <code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">false_</span></code>
otherwise (See <a href="../../../../../../../../libs/mpl/doc/refmanual/integral-constant.html" target="_top">MPL
Boolean Constant</a>).
</p>
</td>
</tr>
</tbody>
</table></div>
<a name="spirit.qi.reference.parser_concepts.parser.postcondition"></a><h6>
<a name="id883102"></a>
<a class="link" href="parser.html#spirit.qi.reference.parser_concepts.parser.postcondition">Postcondition</a>
</h6>
<p>
Upon return from <code class="computeroutput"><span class="identifier">p</span><span class="special">.</span><span class="identifier">parse</span></code> the following post conditions
should hold:
</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
On a successful match, <code class="computeroutput"><span class="identifier">f</span></code>
is positioned one past the last matching character/token.
</li>
<li class="listitem">
On a failed match, if a <code class="computeroutput"><span class="identifier">skip</span></code>
parser is <code class="computeroutput"><span class="identifier">unused</span></code>,
<code class="computeroutput"><span class="identifier">f</span></code> is restored to
its original position prior to entry.
</li>
<li class="listitem">
On a failed match, if a <code class="computeroutput"><span class="identifier">skip</span></code>
parser is not <code class="computeroutput"><span class="identifier">unused</span></code>,
<code class="computeroutput"><span class="identifier">f</span></code> is positioned one
past the last character/token matching <code class="computeroutput"><span class="identifier">skip</span></code>.
</li>
<li class="listitem">
On a failed match, <code class="computeroutput"><span class="identifier">attrib</span></code>
is left untouched.
</li>
<li class="listitem">
No post-skips: trailing <code class="computeroutput"><span class="identifier">skip</span></code>
characters/tokens will not be skipped.
</li>
</ul></div>
<a name="spirit.qi.reference.parser_concepts.parser.models"></a><h6>
<a name="id883247"></a>
<a class="link" href="parser.html#spirit.qi.reference.parser_concepts.parser.models">Models</a>
</h6>
<p>
All parsers in Spirit.Qi are models of the <span class="emphasis"><em>Parser</em></span>
concept.
</p>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright © 2001-2010 Joel de Guzman, Hartmut Kaiser<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
</p>
</div></td>
</tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="../parser_concepts.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../parser_concepts.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="primitiveparser.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a>
</div>
</body>
</html>
